Nanotechnology Plasma & Nanotechnology Graphene nanoflakes - - PowerPoint PPT Presentation

Nanotechnology

Plasma & Nanotechnology

Graphene nanoflakes CNT Si nanofibers Au nanodots

Nano-Patterns

Good and fast Start

▪ References:

▪ PRINCIPLES OF PLASMA DISCHARGES AND MATERIALS PROCESSING, MICHAEL A. LIEBERMAN & ALLAN J. LICHTENBERG, John Wiley & Sons, Inc (2005). ▪ PHYSICS OF RADIO-FREQUENCY PLASMAS, PASCAL CHABERT & NICHOLAS BRAITHWAITE, Cambridge University Press (2011). ▪ Spacial issue „ Plasma and Nanotechnology“ : , J. Phys. D: Appl.

• Phys. 44 (2011)

Plasma ball

Low Temperature Plasma

▪ Low degree of ionization ▪ Neutral background the ion and electron density ▪ Collisions with the background gas is dominant compared to electron ion collisions ▪ Non-equilibrium plasmas at low pressures

Various applications

Plasma cleaning

Is it really hot?

Does the ocean water temp. change?

Plasma Chemistry I

▪ Dissociation of feedstock gas into active neutral free radicals: ▪ Dissociation of the free radicals

Plasma Chemistry II

▪ Dissociative ionization and attachment: ▪ Chlorine discharge

Plasma Chemistry III

▪ Chemical reactions between neutrals in the presence of a third body ▪ ▪ At the substrate ▪ Removing ▪ Etching ▪ Deposition or growth

Plasma Etching

▪ An etched profile with ▪ 0.5 micrometer (500 Nanometer) wide ▪ 4 micrometer (4000 nanometer) ▪ Such profiles are used for device isolation and charge storage capacitores.

▪ Human hair is 50-100 micrometer in diameter.

Plasma Etching steps I

a) Metal Deposition b) Photoresist deposition c) Optical exposure through a pattern d) Photoresist development

Plasma Etching steps II

e) Anisotropic etching f) Photoresist removal

▪ Process Selectivity: ▪ Depends on the plasma species ▪ Energy threshold & energy activation

Wet and Dry etching

▪ Carbon Floride (CF4) does not react with Silicin (Si). ▪ Dissociative ionization and attachment: ▪ Wet etching ▪ Dry etching: Accelerate CF3

+ toward the Silicon substrate

Plasma Etching steps II

Wet etching Chemical etching Dry etching

Ion enhanced plasma etching

New world of integrated circuits?

New world of integrated circuits?

Deposit or grow Oxygen & Argon Plasma: Deposition of SiO2 on Si Deposition of Aluminum, Tungsten, superconducting films SiH2Cl2/NH3 & Si(OC2H5)4/O2 Plasma: Deposition of Si3N3 and SiO2

New world of integrated circuits?

Doping and modification BF3 discharge: Implant dopant B atoms into Silicon

New world of integrated circuits?

Etching and removing CF4/Cl2/O2 discharges: Selectively remove silicon films

O2 discharge: Remove photoresist and polymer films

Devices

Plasma electronics, Applications in Microelectronic Device Fabrication

▪ Capacitive coupled plasma are used in plasma etching and deposition process for production of: ▪ Integrated circuits ▪ Sollar cells

Capacitive coupled plasma

Symmetric discharge

▪ The ion flux and the ion energies increase (decreases) by increasing (decreasing) the deriving frequency.

CCPs & blocking a Capacitor

Geometrically Asymmetric

▪ The RF current is constant. ▪ But the ground electroge Area is greater then the powered electrode area.

▪ The blocking capacitor blocks DC currents:

Particle and Potential distribution

Electrically Asymmetric

▪ The high frequency controls the ion plasma bulk (ion flux). ▪ The lower frequency controls the plasma sheath. ▪ The phase shift between the two sources controls also the sheath potential. ▪ The independent control is not always perfect.

Magnetron

Magnetic Asymmetry

High density sources (ICP)

High density sources (ECR)

Typical CCP parameters

What are optimum plasma etching parameters?

The anistropy of the etching profile

• The etching profile is mainly determined by

the ion flux, the ion energy, and the ion angular distribution.

• High aspect ratio could be achieved

employing narrower ion angular distribution.

• Assuming an etching profile as a hole, the

aspect ratio is the ratio of the height of the hole to the diameter of the hole; AR=H/D. ▪ The direct ion heat flux hits the bottom of the contact is given by ▪ The direct ion heat flux which a combination

• f the angular distribution and the ion energy

distribution is given as where 2Θ is the angle

• f view : tan (Θ)=D/2H

H D 2Θ Contact Hole

IAD [# m^-2 s^-1 deg^-1] Angle [deg]

Sheath potential (I)

◼ Increasing the sheath potential

increases the ion drift velocity normal to the electrode with respect to the ion velocity components parallel to the electrode, the result the angle of the maximum ion flux shifts toward zero.

◼ Sinsolidal electrode potential

Sheath potential (II)

◼ Increasing the sheath potential

increases the ion drift velocity normal to the electrode with respect to the ion velocity components parallel to the electrode, the result the angle of the maximum ion flux shifts toward zero.

◼ Sinsolidal electrode potential

Ion Flux (I)

◼Because it is really difficult to interpret

the results of numerical models, it is necessary sometimes to use simple analytical models or available measurements.

◼Lieberman’s model (*) is restricted to

high frequency regime, however, it predicts that the high ion fluxes enter the sheath leads to thinner sheaths.

◼This qualitatively agree with the

simulation results.

◼Back to the simulation results, Higher

ion fluxes leads to thinner sheaths, narrower IAD, higher Direct ion flux and ion heat flux. *M.A. Liebermann, IEEE, 16 (1988) 638 equation(27).

Ion Flux (II)

◼Because it is really difficult to interpret

the results of numerical models, it is necessary sometimes to use simple analytical models or available measurements.

◼Lieberman’s model (*) is restricted to

high frequency regime, however, it predicts that the high ion fluxes enter the sheath leads to thinner sheaths.

◼This qualitatively agree with the

simulation results.

◼Back to the simulation results, Higher

ion fluxes leads to thinner sheaths, narrower IAD, higher Direct ion flux and ion heat flux. *M.A. Liebermann, IEEE, 16 (1988) 638 equation(27).

Gas Pressure (I)

◼ Increasing the background gas

pressure broads the IADs.

◼ The scatter of ions decreases the

direct ion flux and the direct ion heat flux at all aspect ratios.

Gas Pressure (I)

◼ Increasing the background gas

pressure broads the IADs.

◼ The scatter of ions decreases the

direct ion flux and the direct ion heat flux at all aspect ratios.

Direct Ion heat flux

◼ Direct ion heat flux at the bottom of a

profile with dimensions :

– depth of 100 nm. – Width of 5 nm.

Aluminum Oxide Deposition I

Aluminum Oxide Deposition II

Graphene

▪ It is a single layer of Carbon atoms arranged i a hexagonal lattice ▪ Zero band gap material ▪ The strongest material: 200 times steel ▪ Conducts heat and electricity effeciently ▪ Transparent ▪ Nonlinear diamagnetism

Graphene applications

Unbreakable smart phones Computer chip faster 10000 than normal chip Batteries and super capacitors Storage more energy Charge faster Low cost solar cells Bone Tissue engineering Drug delivery Remove radioactive materials from water

Carbone nanotube

Carbone nanotube

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